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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id s13sm3841034edr.86.2021.04.01.08.57.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 01 Apr 2021 08:57:34 -0700 (PDT) Subject: Re: [PATCH v2 2/2] KVM: nSVM: improve SYSENTER emulation on AMD To: Vitaly Kuznetsov , Maxim Levitsky , kvm@vger.kernel.org Cc: Wanpeng Li , Jim Mattson , Ingo Molnar , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , "H. Peter Anvin" , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Thomas Gleixner , Borislav Petkov , Sean Christopherson , Joerg Roedel References: <20210401111928.996871-1-mlevitsk@redhat.com> <20210401111928.996871-3-mlevitsk@redhat.com> <87h7kqrwb2.fsf@vitty.brq.redhat.com> <6f138606-d6c3-d332-9dc2-9ba4796fd4ce@redhat.com> <87zgyic984.fsf@vitty.brq.redhat.com> From: Paolo Bonzini Message-ID: Date: Thu, 1 Apr 2021 17:57:33 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <87zgyic984.fsf@vitty.brq.redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/04/21 17:31, Vitaly Kuznetsov wrote: >>>> + svm->sysenter_eip_hi = guest_cpuid_is_intel(vcpu) ? (data >> 32) : 0; >>> (Personal taste) I'd suggest we keep the whole 'sysenter_eip'/'sysenter_esp' >>> even if we only use the upper 32 bits of it. That would reduce the code >>> churn a little bit (no need to change 'struct vcpu_svm'). >> Would there really be less changes? Consider that you'd have to look at >> the VMCB anyway because svm_get_msr can be reached not just for guest >> RDMSR but also for ioctls. >> > I was thinking about the hunk in arch/x86/kvm/svm/svm.h tweaking > vcpu_svm. My opinion is not strong at all here) Ah okay, if it's just that I would consider the change a benefit, not a problem with this patch. Paolo